required by the purpose of the project and that the  compilation  be  completed  with  sufficient  lead time.  Generally,  a  separate  folder  for  each  project is maintained and labeled. Some  of  the  engineering  data  that  may  be considered for SEABEE projects are as follows: Vicinity  maps,    topographic  maps,  or aerial  photographs  of  the  site Geographic   factors,   accessibility,   real estate,  and  so  forth Geographic   location:   latitude   and longitude;   control   points   (both   horizontal   and vertical) Tide   information Weather and climatic conditions: rainfall, wind velocity (including direction and duration), flood, and perhaps typhoon or hurricane seasons Current  velocity  and  discharge  of  a  river or   stream   and   perhaps   an   estimate   of   the watershed  area Types  of  soils  and  their  natural  conditions (samples  may  be  collected  for  testing) Availability  of  construction  materials,  such as  rocks,  gravel,  sand,  borrow  pits,  and  timber, near  the  site Availability  and  suitability  of  local  labor and existing facilities, such as sources of power, water, and other utilities Other  factors  affecting  construction, military  operations,  and  logistics  support Factors Affecting Fieldwork The surveyor must constantly be alert to the different   conditions   encountered   in   the   field. Physical    factors, such   as   TERRAIN   AND WEATHER   CONDITIONS,   affect   each   field survey in varying degrees. Measurements using telescopes  can  be  stopped  by  fog  or  mist.  Swamps and  flood  plains  under  high  water  can  impede taping surveys. Sights over open water or fields of  flat,  unbroken  terrain  create  ambiguities  in measurements using microwave equipment. The lengths of light-wave distance in measurements are   reduced   in   bright   sunlight.   Generally, reconnaissance will predetermine the conditions and alert the survey party to the best method to use  and  the  rate  of  progress  to  expect. The STATE OF PERSONNEL TECHNICAL READINESS  is  another  factor  affecting  field- work.  As  you  gain  experience  in  handling  various surveying  instruments,  you  can  shorten  survey time  and  avoid  errors  that  would  require  resurvey. The PURPOSE AND TYPE OF SURVEY are primary   factors   in   determining   the   accuracy requirements.    First-order   triangulation,   which becomes the basis or “control” of future surveys, is made to high-accuracy standards. At the other extreme,  cuts  and  fills  for  a  highway  survey  carry accuracy  standards  of  a  much  lower  degree.  In some construction surveys, normally inaccessible distances   must   be   computed.   The   distance   is computed  by  means  of  trigonometry,  using  the angles  and  the  one  distance  that  can  be  measured. The  measurements  must  be  made  to  a  high  degree of  precision  to  maintain  accuracy  in  the  computed distance. So,  then,  the  purpose  of  the  survey  determines the  accuracy  requirements.  The  required  accuracy, in turn, influences the selection of instruments and procedures. For  instance,  comparatively  rough procedures   can   be   used   in   measuring   for earthmoving, but   grade   and   alignment   of  a highway  have  to  be  much  more  precise,  and  they, therefore, require more accurate measurements. Each  increase  in  precision  also  increases  the  time required  to  make  the  measurement,  since  greater care  and  more  observations  will  be  taken. Each survey measurement will be in error to the extent that no measurement is ever exact. The errors are classified as systematic and accidental and are explained in the latter part of this text. Besides   errors,   survey   measurements   are   subject to  mistakes  or  blunders.  These  arise  from misunderstanding  of  the  problem,  poor  judgment, confusion on the part of the surveyor, or simply from an oversight. By working out a systematic procedure,  the  surveyor  will  often  detect  a  mistake when  some  operation  seems  out  of  place.  The procedure will be an advantage in setting up the equipment, in making observations, in recording field  notes,  and  in  making  computations. Survey speed is not the result of hurrying; it is the result of saving time through the following factors: 1.  The  skill  of  the  surveyor  in  handling  the instruments 2.  The  intelligent  planning  and  preparation  of the work 11-5